A wind turbine comprises a rotor with rotor blades and a hub. The hub of the wind turbine is connected to the nacelle of the wind turbine. The hub is connected to the main shaft of the wind turbine or to the rotor of an electrical generator at a direct driven wind turbine.
The hub is attached to the nacelle by a flange connection. The flange connection between the hub of a wind turbine and the nacelle comprises a flange at the hub of the wind turbine and a flange at the nacelle of the wind turbine
The hub sided flange and the nacelle sided flange are connected together by bolts. The bolts press the flanges together to prevent any movement of one of the flanges in relation to the other flange.
During the operation of the wind turbine the wind interacts with the rotor blades of the wind turbine and rotates the rotor. Due to the wind and gusts in the wind varying loads and vibrations are induced into the rotor.
The flange connection transfers the rotation to the main shaft of the wind turbine or to the rotor of the electrical generator. In addition radial forces, axial forces and bending moments from the loads and vibrations are transferred from the hub to the nacelle.
As the development of the wind turbine advances to bigger rotor diameters, more and more loads and vibrations have to be transferred over the flange connection.
It is known to increase the number and diameter of the bolts in the flange connection to prevent movements between the two flanges.
This shows the disadvantage, that more and heavier bolts are needed in a wind turbine and more installation time is needed for tightening the bolts.